1. Technical Field
The present invention relates to an ink jet ink set and an ink jet recording system.
2. Related Art
Heretofore, recording employing an ink jet recording method has been performed by supplying ink to a print head, discharging small ink droplets to cause the small ink droplets to fly to thereby make the small ink droplets adhere onto recording media, such as paper. When discharging the ink, poor discharge sometimes occurs due to the generation of air bubbles in the ink and the like. Then, various techniques of degassing the ink using a degassing device or the like to remove the air bubbles to thereby stably discharge the ink have been proposed.
For example, JP-A-2011-42104 aims at providing an ink jet image forming method which includes continuously supplying a large amount of ink in just proportion to an ink head which drives at a high frequency and also in which destabilization of ink discharge from the ink head due to cavitation generated in the ink supply, image defects caused thereby, and a reduction in density are suppressed. JP-A-2011-42104 discloses an ink jet image forming method including transferring an ink, which is an aqueous dye ink containing an aqueous dye, ion exchanged water, and an organic solvent, having a surface tension of 45 mN/m or more, and having a number of contained solid particles filtered through a filtration material with a filtration accuracy of 0.5 μm and having a particle diameter as measured by a particle counter of 0.5 μm or more of 10000 (pieces/10 ml) pieces or less, from an ink container to a storage tank once, pumping the ink with a liquid feed pump, supplying the ink as it is or after filtering the ink with a filtration material with a filtration accuracy of 0.5 μm to an ink jet head through a degassing device in a state where, as the number of the contained solid particles, the number of the contained solid particles having a particle diameter as measured by a particle counter of 0.5 μm or more is 10000 (pieces/10 ml) or less, and then discharging the ink from the ink jet head to a printing medium to form an image on the printing medium.
However, a commercially-available ink tank is relatively less expensive but, in the commercially-available ink tank, ink and air contact each other due to the structure. Even when an open type ink cartridge which is generally used as a commercially-available ink cartridge is charged with degassed ink, the air gradually dissolves into the ink. When the degassed ink disclosed in JP-A-2011-42104 passes through the ink tank and the open-type ink cartridge described above, air dissolves into the ink, and therefore the degassing becomes meaningless, which results in a problem in that poor discharge occurs.
As the causes of the poor discharge, not only air bubbles but clogging of nozzles which discharges ink is also mentioned. Therefore, the use of an ink which is excellent in clogging resistance is an also important. When the poor discharge occurs, the weight of ink droplets adhering to a recording medium does not reach a desired weight, and, as a result, the color reproduction properties sometimes decrease.